The present invention relates to a scannable mirror for an interferometer.
Optical spectroscopy is a sensitive and selective method of detecting and identifying molecules. It is rapid and requires little or no sample preparation, and is amenable to continuous and real-time monitoring. Optical spectroscopy has many applications, including the detection of chemical and biological materials, the determination of a person""s metabolic status, the monitoring of drinking water purity, and other analytical applications. Known optical coherence interferometry utilizes a mirror that scans back and forth rapidly (e.g., at 30-100 Hz) over a small distance (e.g., about 1 mm or less), but is not susceptible to being used in a miniature instrument. In spite of its power, optical spectroscopy is not widely used because spectrometers with useful resolution are laboratory instruments that are too big, too fragile, and too sensitive to vibration, to be utilized in uncontrolled environments, such as might be encountered if the instrument were to be taken into the field. Moreover, a cryogenically-cooled detector is often required, which presents a problem for use outside of the laboratory.
Interferometric Raman spectrometry has been proposed with single-mode optical fiber elements, e.g., see H. I. Heaton, xe2x80x9cInterferometric Raman Spectrometry with Fiber Waveguides,xe2x80x9d Applied Optics, Vol. 36, No. 27, 20 Sep. 1997, pages 6739-6750. Single-mode optical fibers, however, tend to be more expensive and more sensitive to physical effects than are multi-mode optical fibers, and the proposed instrument is reported as not yet practical. Problems of scanning linearity and reproducibility are reported for the as yet laboratory-grade system. Id. at page 6749. In addition, the use of single-mode optical fiber avoids the modal dispersion caused by multi-mode optical fiber and the effect of the modal dispersion that tends to degrade the resulting spectrum of the sample being measured.
Thus, there is a need and desire for a scannable mirror for an optical interferometer or spectrometer that is rugged and small, and that can provide high spectral resolution. It would also be desirable that scanning mirror arrangement be suitable for use in a hand-held spectrometer.
To this end, the scannable mirror of the present invention comprises a mirror disposed in an optical waveguide facing a first end thereof and moveable therein toward and away from the first end thereof, and a motor moving the mirror in the optical waveguide toward and away from the first end of the optical waveguide,